Detecting ice particles

ABSTRACT

Systems and methods for detecting ice particle accumulation is disclosed herein. In one exemplary implementation, a method for detecting ice is described in which a parameter within an interior volume of a heated conduit is measured. The method also includes detecting the presence of an accumulation of ice particles based on the parameter measured within the interior volume of the heated conduit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 12/442,833, filedMar. 25, 2009 which is a §371 filed application, and claims priority toPCT/US07/79328, filed Mar. 25, 2009, which claims the benefit ofpriority to U.S. Provisional Application No. 60/826,827, filed Sep. 25,2006, all of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to detecting ice and moreparticularly relates to systems and methods for detecting and measuringthe accumulation of ice particles when an aircraft is in flight.

BACKGROUND

Atmospheric conditions that are important to designers of airbornevehicles include liquid water content (LWC) and ice water content (IWC).While LWC has for some time been the focus of sources of hazardous icedue to the freezing of supercooled liquid water on aircraft surfaces,attention recently has been directed to the ice content of theatmosphere and potential hazardous accumulation of ice particles. Theseparticles may be in the form of individual ice crystals, aggregates ofcrystals such as snowflakes, or crystals that have collided withsupercooled water droplets to form more dense and spherical particlessuch as graupel and hail. The size of ice particles can varysignificantly, from microns to centimeters. In the past, ice particlesgenerally were not considered to be a hazard to the outside shell of anaircraft because they will typically bounce off the surface of theaircraft and not accumulate. Ice particles can nonetheless causeproblems associated with an aircraft. For example, when ice particlesare ingested into an aircraft's engines, ducts, or cavities, they cancollect together and form a blockage that can be detrimental. Also,accumulated ice particles can melt and then refreeze within a downstreamportion of the aircraft's systems, further causing problems to enginesand/or air data instrumentation. To help assess these potentialproblems, the FAA has created an Ice Protection Harmonization WorkingGroup that among other activities investigates engine events attributedto ice particle ingestion.

A need exists in the current state of the art to detect the accumulationof ice particles, and to detect ice particles that are present insufficient concentration for a sufficient time period, since asubstantial concentration of ice may have a hazardous impact on airbornevehicles.

SUMMARY

Generally, the present disclosure describes systems and methods fordetecting ice particles. In one embodiment, among others, a system isdescribed for detecting ice particles for use on an airborne vehicle.The system comprises a conduit having a longitudinal axis substantiallyparallel with a flow of air. The conduit includes an inlet at a foreportion thereof and an outlet at an aft portion thereof. The system alsoincludes a sensor configured to detect when an accumulation of iceparticles at least partially clogs the outlet of the conduit. Also, thesensor is further configured to provide an indication signal when anaccumulation of ice particles is detected. The system also comprises aprocessing device in communication with the sensor and a heaterconfigured to heat the conduit to a temperature that can melt the iceparticles. The cross-sectional area of the inlet is larger than thecross-sectional area of the outlet, such that ice particles in the flowof air can accumulate at the outlet of the conduit.

In one of several implementations, a conduit used in an ice detectingdevice is disclosed herein. The conduit in this one embodiment comprisesa hollow tube having a channel through which air is capable of flowing.The conduit also includes an inlet located at a first end of the hollowtube. The inlet is configured to allow air to enter the channel and hasa first cross-sectional area. Also included in the conduit is an outletlocated at a second end of the hollow tube. The outlet is configured toallow air to exit the channel and has a second cross-sectional area. Thefirst cross-sectional area is greater than the second cross-sectionalarea such that an obstruction is formed within the channel when theconcentration of ice particles in an airflow exceeds a threshold level.

The present application also includes implementations of methods fordetecting ice particles. In one embodiment, a method of detecting ice inthe vicinity of an airborne vehicle is disclosed. The method comprisesheating a conduit at a selected power level and measuring a parameterwithin an interior volume of the conduit. The method also includesdetecting the presence of an accumulation of ice particles based on theparameter measured within the interior volume of the conduit.

Also disclosed herein are embodiments of software program(s) formeasuring ice accumulation. In one implementation, a program is storedon a computer-readable medium and comprises logic configured to receivea measurement of a parameter of an interior portion of a conduit. Theconduit includes an inlet having a first cross-sectional area and anoutlet having a second cross-sectional area. The first cross-sectionalarea is greater than the second cross-sectional area. The program alsoincludes logic configured to process the parameter of the interiorportion of the conduit to detect when ice particles obstruct the outletof the conduit.

Other features, advantages, and implementations of the presentdisclosure, not expressly disclosed herein, will be apparent to one ofordinary skill in the art upon examination of the following detaileddescription and accompanying drawings. It is intended that such impliedimplementations of the present disclosure be included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the following figures are not necessarily drawn toscale. Instead, emphasis is placed upon clearly illustrating the generalprinciples of the present disclosure.

Reference characters designating corresponding components are repeatedas necessary throughout the figures for the sake of consistency andclarity.

FIG. 1 is a diagram illustrating an oblique view of an ice detectiondevice according to one embodiment.

FIG. 2 is a schematic diagram of a first embodiment of an ice detectionsystem.

FIG. 3 is a schematic diagram of a second embodiment of an ice detectionsystem.

FIGS. 4A-4C illustrate exemplary embodiments of a conduit, such as oneof the conduits shown in FIGS. 2 and 3.

FIG. 5 is a diagram of a first embodiment of a sensing element, such asone of the sensing elements shown in FIGS. 2 and 3.

FIG. 6 is a diagram of a second embodiment of a sensing element, such asone of the sensing elements shown in FIGS. 2 and 3.

FIG. 7 is a diagram of a third embodiment of a sensing element, such asone of the sensing elements shown in FIGS. 2 and 3.

FIG. 8 is a diagram of a fourth embodiment of a sensing element, such asone of the sensing elements shown in FIGS. 2 and 3.

FIG. 9 illustrates a flow chart for detecting ice particles according toone embodiment.

DETAILED DESCRIPTION

When an aircraft is in flight, ice particles can build or gather on orin various components and systems of the aircraft. This collection orformation of ice is undesirable and can obstruct or restrict airflow andimpede the operation of the components and systems. Taking advantage ofthis tendency of ice to accumulate, the present disclosure describessystems and methods for providing a warning or indication when iceparticle accumulation reaches a level that can negatively affect theoperation of the aircraft components and systems. In response to awarning of excess levels of ice, corrective actions could then be takento reduce or even avoid disruption. The warnings or indications can beprovided to the crew of the aircraft to prompt the crew to take actionor they can be provided to external devices, such as deicing devices,which can be configured to automatically take action in response to thewarnings.

FIG. 1 illustrates an exemplary embodiment of an ice detection device10. The ice detection device 10 includes a first converging conduit 12,a second converging conduit 14, a strut 16, a base 18, a housing 20, anda connector 22. The ice detection device 10 can be mounted on anaircraft (not shown) for detecting ice particles in the airflow when theaircraft is in flight. In some embodiments, the first converging conduit12 and second converging conduit 14 are substantially equal in size andgeometry. Also, the first and second converging conduits 12, 14 may bepositioned near each other or in locations that may experience similarairflow patterns. In addition, the first and second converging conduits12, 14 may be oriented in substantially the same direction, or at leastin similar directions with respect to airflow. As illustrated, the firstand second converging conduits 12, 14 are positioned at approximatelythe same height above the base 18. It should be noted, however, that thetwo converging conduits 12, 14 may have any relative position suitableto experience similar airflow patterns with respect to the aircraft.When designed with the proper dimensions and installed with the properorientation, the converging conduits 12, 14 can, by design, purposelyaccumulate ice particles. Also, aerodynamic forces can keep theaccumulation in contact with the inner walls of the converging conduits12, 14.

The base 18 can include holes around its perimeter that allow the icedetection device 10 to be attached to the outer shell of the aircraft.In this case, the ice detection device 10 may be attached to theaircraft using nuts, bolts, rivets, etc., or, in other embodiments, maybe attached to the aircraft using any other suitable attachmentcomponents. The base 18 also serves to keep the ice detection device 10in a fixed position with respect to the aircraft. The ice detectiondevice 10 may be attached to the fuselage, wing, tail, engine inlet, orother part of the aircraft. The mounting location of the ice detectiondevice 10 may be based on the aerodynamics, temperature characteristics,vibration characteristics, and the availability of additional air datameasurements made by external devices.

The housing 20 may house a number of electronic components, as describedin more detail below, which can be configured to detect measurableparameters, process signals, and control components in a feedbackmanner. In other embodiments, these electronic components may bepositioned outside the housing 20 in portions of the structure of theice detection device 10 above the base 18 or at remote locations withinthe interior portions of the aircraft. The connector 22 includes anysuitable adapting structure, pins, terminals, etc., for electricallycommunicating (either via wires or wireless transmission) detectionsignals, warning signals, alarm signals, etc., to other devices, e.g.,deicing devices.

FIG. 2 is a diagram showing a first embodiment of an ice detectionsystem 24. The ice detection system 24 includes a conduit 26, a sensingelement 28, a transducer 30, a signal processing system 32, and aheating element 34. The conduit 26 is supported on an aircraft (notshown) by a strut 36, having any suitable size and shape. The strut 36holds the conduit 26 in a steady position such that a longitudinal axisof the conduit 26 is substantially aligned with the flow of air withrespect to the aircraft as it is in flight. Depending on the airflowcharacteristics around various portions of the aircraft, the conduit 26may be aligned in any suitable direction such that air flows into aninterior portion of the conduit 26. In some embodiments, thelongitudinal axis of the conduit 26 is substantially aligned with thedirection in which the aircraft is moving, that is, when the conduit 26is positioned near a portion of a surface of the aircraft where airflowover that portion is substantially aligned with the aircraft flightdirection. The strut 36 may be heated electrically or by other means toallow it to operate ice-free in flight.

The conduit 26 includes a fore portion 38 where air enters the conduitand an aft portion 40 where air exits the conduit. The cross-sectionalarea of the fore portion 38 can be larger than the cross-sectional areaof the aft portion 40, such that, in a sense, the conduit 26 funnels theair flowing therethrough. While conduit 26 is shown in FIG. 2 as atruncated cone, this invention is not limited thereby. When the airincludes a certain concentration of ice particles, the ice particles mayaccumulate in the aft portion 40 of the conduit 26 and create a clog orblockage. When this happens, an increase occurs in the static airpressure at points along the interior wall of the conduit 26, hereafterreferred to as “wall pressure.”Also, other parameters within theinterior of the conduit 26 may change as well. The sensing element 28senses the changes in the parameters of the interior of the conduit 26due to the ice particle obstruction or blockage.

The sensing element 28 provides the sensed or measured parameter to thetransducer 30, which converts the sensed parameter into a correspondingelectrical signal. In some embodiments, the sensing element 28 andtransducer 30 may be combined to form a unitary sensing device forsensing a particular parameter. The transducer 30 may include a filtercircuit to suppress noise and/or electromagnetic interference. Thetransducer 30 may also include other electrical circuits, such asanalog-to-digital converters, etc. After converting the sensed parameterinto an electrical signal, the transducer 30 provides this signal to thesignal processing system 32.

The signal processing system 32 may include, for example, amicroprocessor or microcontroller, memory components, etc. The memorycomponents may include internally fixed storage and/or removable storagemedia. The storage within the memory components may include volatileand/or non-volatile memory and can store a software program in read onlymemory (ROM) that includes logic for measuring or detecting theconcentration of ice particles in an airflow. The microprocessor of thesignal processing system 32 can execute the software to perform relatedfunctions for measuring the ice concentration. Logic may be includedthat regulates the application of power to the heating element 34 forincreasing or decreasing the temperature of the heating element 34 and,in turn, the temperature of the conduit 26. Logic may also be includedthat processes measured parameters of the interior of the conduit 26 andstores changes of the parameters over time. Logic may also be includedthat communicates with external devices for controlling a remote displayscreen or indicating parameters or conditions to aircraft avionics. Whenthe signal processing system 32 detects that ice accumulation is severeenough to disrupt operation of aircraft components and systems, thesignal processing system 32 provides an advanced warning so thatcorrective action can be taken.

The signal processing system 32 can be configured to receive otherparameters or characteristics of ambient air, gathered, for instance, byan external device. These other parameters may include, for example,total temperature, total pressure, static pressure, airspeed, altitude,humidity, etc. These parameters could be used to calculate variations inconvective heat removal and ambient temperature influences on theconduit 26 such that heating power could be adjusted to ensure that anice clog might accumulate at a certain ice particle concentration level.

The signal processing system 32 may also include a low power supplydevice for applying power to its internal circuitry plus a high powersupply device for applying power to the heating element 34. For example,the power applied to the heating element 34 may be on the order of up toabout 300 watts. The signal processing system 32 can adjust the amountof power to control the rate at which accumulated ice melts.

In general, heating power would be decreased with increasing airtemperature and/or decreasing mass air flow over the sensing element 28.The amount of power adjustment could be defined by an algorithm orlook-up table stored in memory of the signal processing system 32. Thealgorithm or look-up table could be defined by calibration of thesensing element 28 at a number of conditions where various air datainformation, such as temperature, pressure, air flow, etc., is known.Such calibration, for instance, could be performed in a wind tunnel.

Although the heating element 34 is shown in FIG. 2 as covering only asmall section of the conduit 26, it should be understood that theheating element 34 may be designed to partially or completely surroundthe conduit. Also, the heating element 34 can be positioned outside theconduit 26, embedded within the wall material of the conduit 26, orpositioned adjacent to an interior surface of the conduit 26. Theheating element 34 is heated to a temperature to prevent supercooledliquid water from freezing. When heated to a higher temperature, theheating element 34 slows down the rate at which ice particles canaccumulate within the conduit 26. An ice accumulation is typicallymaintained as long as ice particles enter the conduit 26 at a greaterrate than the heating element 34 can melt the ice.

To prevent freezing of supercooled liquid water in the most severetemperature conditions, the heating element 34 will need to heat thesupercooled liquid water, possibly as high as a 40° C. temperaturedifferential. The energy needed to heat a mass of ice by a certaintemperature differential is greater than the energy needed to heat thesame mass of supercooled liquid water by the same temperaturedifferential. For example, the heat of fusion of ice is about two timesgreater than would be required to warm the same mass of supercooledwater from an initial temperature to a final temperature that isslightly more than 40° C. higher than the initial temperature.Furthermore, atmospheric ice mass content usually considered harmfulexceeds water mass content by several times. For reference, one to twograms of water per cubic meter of air is usually considered to be a highliquid water content whereas five to eight grams of ice particles percubic meter is usually considered to be a high ice content. Thisillustrates that it will take significantly more energy to melt an iceclog relative to the amount of energy to keep the conduit 26 operatingice-free in a supercooled liquid water environment. The controlledheating of the surfaces of the conduit 26 can keep the conduit ice-freein LWC conditions and ice-free when the IWC concentration is below acertain threshold. However, as designed, the conduit 26 can clog when acertain concentration of ice particles exceeding the threshold isexperienced. Often aircraft are equipped with ice detectorssubstantially sensitive to LWC only. Icing rate information from one ofthese detectors could be used to discriminate a very high LWC conditionfrom a relatively low IWC condition if it were desired to extend therange of the ice crystal detector to a lower detection threshold thanwould otherwise be possible.

FIG. 3 is a schematic diagram of a second embodiment of an ice detectionsystem 42. In this embodiment, the ice detection system 42 includes twoconduits 44 and 46, two respective sensing elements 48 and 50, atransducer 52, a signal processing system 54, and two respective heatingelements 56 and 58. The conduits 44, 46 are supported by struts 60 and62, respectively, which are connected to an aircraft. In someembodiments, the conduits 44, 46 are supported by a single strut,similar to the implementation illustrated in FIG. 1. The components ofthe ice detection system 42 are similar in function to the correspondingcomponents described with respect to FIG. 2. However, instead of oneconduit in which an ice accumulation can be detected, the ice detectionsystem 42 of FIG. 3 includes two conduits 44, 46. Also, the heatingelements 56, 58 can be heated to different temperatures. In thisrespect, the replenishment rate and melting rate of collected ice withinthe conduits 44, 46 differs from one conduit to the other based on thedifferences in temperature, assuming all other factors are the same.

The ice detection system 42 can detect transitional changes in theparameters of the conduits 44, 46 with respect to each other. Forexample, when both conduits are not clogged and air can flow freelythrough the conduits, the wall pressure within the interior of theconduit 44 is approximately the same as that of conduit 46. When aconduit heated to a lower temperature forms an ice obstruction thatrestricts the flow of air, the pressure inside this conduit increases.The difference in pressure from the clogged conduit to the uncloggedconduit can be detected as a first transition. At a later time, anothertransition may occur such that the obstruction in the one conduit iscleared by melting. Yet another transition may be represented by theinitially unclogged conduit forming a clog such that both conduits wouldbe clogged. In the two latter cases, the pressure difference between theinteriors of the conduits will return to about zero. The signalprocessing system 54 may utilize logic to determine which event hasoccurred by tracking the pressure history of the two conduits or bytaking other air data information into account.

The signal processing system 54 can adjust or maintain the temperatureof each heating elements 56, 58 as needed to create an accumulation andmelting cycle that can be easily measured. By comparing these cycles ofeach conduit 44, 46 at different temperatures, the signal processingsystem 54 can detect ice concentrations that are severe enough todisrupt operation of other components or systems of the aircraft. Thesignal processing system 54 also includes a clock or timing device tomeasure the duration that each conduit 44, 46 is clogged or to measurethe time difference from the clogging of one conduit to the clogging ofthe other.

In one example, conduit 44 is heated to a first temperature and conduit46 is heated to a second temperature that is higher than the firsttemperature. The second temperature may, in some embodiments, be highenough such that conduit 46 rarely or never clogs. Or, the secondtemperature may be adjusted such that ice accumulation might be likelyto occur in conduit 46, but after a time from which conduit 44 clogs.

The signal processing system 32, 54 of the present disclosure can beimplemented in hardware, software, firmware, or a combination thereof.When implemented in software or firmware, an ice detection softwareprogram of the signal processing system 32, 54 can be stored in memoryand executed by a processing device. When implemented in hardware, theice detection software program can be implemented, for example, usingdiscrete logic circuitry, an application specific integrated circuit(ASIC), a programmable gate array (PGA), a field programmable gate array(FPGA), etc., or any combination thereof.

The programs or software code that include executable logicalinstructions, as described herein, can be embodied in any suitablecomputer-readable medium for execution by any suitable processingdevice. The computer-readable medium can include any physical mediumthat can store the programs or software code for a measurable length oftime.

FIGS. 4A-4C illustrate three embodiments, among other possibleembodiments, of conduits having different structural features. Theconduits described with respect to the embodiments of FIGS. 2 and 3 mayhave the structure as shown in these figures or may include any othersuitable structure that may tend to enhance the accumulation of iceparticles. The conduits of FIGS. 4A-4C may include any material orcombination of materials that may be suitable for sufficient strength,durability, and temperature fluctuation that is experienced by anaircraft. In some embodiments, the conduits of FIGS. 4A-4C may includean additional cylindrical extension (not shown) at the outlet of theconduit to reduce the effect of eddy currents at the aft portions of theconduits.

The cross-sectional area at the fore entrance to the conduits can bedefined by A_(f) and the cross-sectional area at the aft exit from theconduits can be defined by A_(a). For example, the ratio A_(f):A_(a) canrange from about 2:1 to about 20:1; however, the conduits can be formedsuch that the ratio A_(f):A_(a) is outside this range. Also, theconduits can have any suitable length L and any suitable L:A_(f) ratio.The cross-sectional geometry of openings at the fore and aft portions ofthe conduits, as well as the cross-sectional geometry of the convergingwalls of the conduit, may be circular, elliptical, square, or any othersuitable shape. The rims or edges of the conduits at the fore and aftportions may be formed in a plane that is perpendicular to alongitudinal axis of the conduit. However, in other embodiments, theedges can be non-planar or can be planar but non-perpendicular to thelongitudinal axis of the conduit.

FIG. 4A shows a first embodiment of a conduit 64. In this embodiment,the conduit 64 includes a fore portion 66 and an aft portion 68. Theconduit 64 has an interior portion 70 that has openings fore and aft.The walls 72 of the conduit 64 converge from the fore portion 66 to theaft portion 68 at a constant angle. In this respect, the conduit 64 mayhave the form of a truncated cone or frustum.

FIG. 4B shows a second embodiment of a conduit 74. In this embodiment,the conduit 74 includes a fore portion 76 and an aft portion 78. Theconduit 74 has an interior portion 80 that has openings fore and aft.The walls 82 of the conduit 74 converge from the fore portion 76 to theaft portion 78 non-linearly, giving the conduit 74 a horn shape.

FIG. 4C shows a second embodiment of a conduit 84. In this embodiment,the conduit 84 includes a fore portion 86 and an aft portion 88. Theconduit 84 has an interior portion 90 that has openings fore and aft.The walls 92 of the conduit 84 converge from the fore portion 86 to theaft portion 88 non-linearly, giving the conduit 74 the shape as shown,which can be compared to a shape of a bottomless bowl or vase.

FIG. 5 illustrates a first embodiment of a sensing element 94 formedintegrally with a conduit. The sensing element 94, for example, may beincorporated into the embodiments of FIGS. 2 and 3. In this embodiment,the sensing element 94 includes a wall portion 96 of a conduit, such asconduit 26, 44, or 46 shown in FIGS. 2 and 3. The wall portion 96 mayhave any shape, e.g., as defined in FIGS. 4A-4C, and defines an interior98 and exterior 100 of the conduit. The sensing element 94 also includesa tube 102 having a channel 104, which is open to the interior 98 of theconduit at an opening or tap 106 in the conduit. The tube 102 may beconnected to the wall portion 96 at any desirable location along theconduit using any suitable attachment structure or mechanism. In thisembodiment, the wall pressure within the interior 98 of the conduit andchannel 104 of the tube 102 can be in fluid communication withtransducer 30, 52, thereby allowing the detection of the wall pressureof the interior 98.

In some embodiments, the transducer 30 shown in FIG. 2 can be adifferential pressure sensor that senses the wall pressure in theinterior of the conduit 26 via the tap 106 (FIG. 5) and a referencepressure. The reference pressure is indicative of a pressure to beexpected when the conduit does not have an ice formation at its aftportion restricting the flow of air therethrough. The transducer 30, inthis respect, senses the difference in pressures, if any, and applies adifferential pressure signal to the signal processing system 32.

Furthermore, the sensing element 94 with the tap 106 can be used as thesensing elements 48 and 50 shown in FIG. 3. In this respect, thetransducer 52 may be a differential pressure sensor that senses the wallpressures from the interiors of the conduits 44 and 46. In thisembodiment, the heating element 58 of conduit 46, which may beconsidered as a reference conduit, heats the conduit 46 to such anextent that accumulation of ice is minimized. Hence, the sensing element50 senses a normal pressure for an unclogged conduit. When conduit 44 isclogged with a collection of ice, the pressure in the interior of thisconduit 44 increases. A differential pressure sensed by the transducer52 can then be measured.

FIG. 6 is a diagram of a second embodiment of a sensing element 108,which can be used in place of the sensing elements 28, 48, and/or 50shown in FIGS. 2 and 3. The sensing element 108 includes the wallportion 96 of a conduit separating its interior 98 from its exterior100. The sensing element 108 also includes a pressure sensor 110positioned within the wall portion 96 such that it is exposed to theinterior 98 of the conduit. The pressure sensor 110 may include anysuitable size, structure, or pressure sensing components as are known inthe art for measuring the wall pressure in the interior 98 of theconduit.

FIG. 7 is a diagram of a sensing element 112 according to a thirdembodiment, in which the sensing element 112 can be used in place of thesensing elements 28, 48, and/or 50 shown in FIGS. 2 and 3. The sensingelement 112 includes the wall portion 96 of a conduit separating itsinterior 98 from its exterior 100. The sensing element 112 also includesa temperature sensor 114 positioned within the wall portion 96 such thatit is exposed to the interior 98 of the conduit. The temperature sensor114 may include any suitable size, structure, or temperature sensingcomponents as are known in the art for measuring the temperature in theinterior 98 of the conduit.

FIG. 8 is a diagram illustrating a sensing element 116 according to afourth embodiment. The sensing elements 28, 48, and/or 50 shown in FIGS.2 and 3 may be replaced by the sensing element 116. In this embodiment,the sensing element 116 includes opposing wall portions 96 of a conduitseparating its interior 98 from its exterior 100. The sensing element116 also includes a light source 118 as is known in the art positionedto be able to radiate a beam of light across the interior 98 of theconduit. Responsive to the light beam is a photoreceptive device 120 asis known in the art capable of detecting the light beam from the lightsource 118. When ice gathers in the conduit to such an extent that theice mass obstructs the light beam, then the photoreceptive device 120 isunable to receive the light beam and can send a signal indicating an iceblockage condition. When the ice does not accumulate to such an extentor the ice is subsequently melted to clear the blockage, then thephotoreceptive device 120 can again detect the light beam to determinethat the blockage is no longer present.

FIG. 9 is a flow chart illustrating a process for detecting iceparticles according to an embodiment of this invention. The flow chartincludes heating a conduit, as indicated in block 122. In block 124, theheating power supplied to the conduit is adjusted, if necessary, to meltaccumulated ice that is below a threshold of, for example, IWC. Thepower also may be adjusted in order to compensate for various aircharacteristics or to adjust the sensitivity of the conduit for moreclearly defining an ice accumulation condition. This adjustment or“tuning” prevents ice from accumulating until certain conditions arepresent or until a certain threshold of IWC, for example, is detected inthe atmosphere.

In block 126, parameters can be measured within the interior volume ofthe conduit. These parameters may include, for example, pressure,temperature, light obstruction, or other various parameters that may beindicative of an ice accumulation condition. In decision block 128, itcan be determined whether or not the measured parameter is within aselected range. A selected range may refer to a condition in which theconduit is not clogged or includes no substantial accumulation of ice,allowing air to freely flow therethrough. When it is determined in block128 that the parameter is within the selected range, the process flow isdirected to block 130, in which an indication is presented that theconduit is unclogged. In block 132, a timer is stopped, if this timerwas indeed started in a prior operation. In block 134, a length of timeis measured from the starting of the timer to the stopping of the timer.The process flow is then fed back to block 124 to repeatedly measure theparameter until it is out of the selected range, which can mean thatabove-threshold ice is present.

When it is determined in block 128 that the parameter is not within theselected range, the process flow is directed to block 136. In block 136,an indication is provided that an accumulation of ice particles ispresent within the conduit. In block 138, the timer is started, if itwas indeed stopped, the starting of the timer marking the beginning ofthe time period during which the conduit was clogged. From block 138,the process may then flow back to block 124. The flow chart may beconfigured to continue to loop in this manner to repeat the icedetection operations, or alternatively may discontinue as desired.Additionally, total water content (TWC) could be estimated by adding IWCas determined herein to LWC as determined from an icing conditiondetector.

It should be understood that the steps, processes, or operationsdescribed herein may represent any module or code sequence that can beimplemented in software or firmware. In this regard, these modules andcode sequences can include commands or instructions for executingspecific logical steps, processes, or operations within physicalcomponents. It should further be understood that one or more of thesteps, processes, and/or operations described herein may be executedsubstantially simultaneously or in a different order than explicitlydescribed, as would be understood by one of ordinary skill in the art.

The embodiments described herein merely represent exemplaryimplementations and are not intended to necessarily limit the presentdisclosure to any specific examples. Instead, various modifications canbe made to these embodiments as would be understood by one of ordinaryskill in the art. Any such modifications are intended to be includedwithin the spirit and scope of the present disclosure and protected bythe following claims.

1. An ice particle detection system, for use on an airborne vehicle,comprising: a conduit having a longitudinal axis substantially parallelwith a flow of air containing ice particles, the conduit including aninlet at a fore portion thereof and an outlet at an aft portion thereof;a sensor configured to detect when an accumulation of ice particles atleast partially clogs the outlet of the conduit and further configuredto provide an indication signal when an accumulation of ice particles isdetected; a processing device in communication with the sensor; and aheater configured to provide heating power sufficient to heat theconduit; wherein the cross-sectional area of the inlet is larger thanthe cross-sectional area of the outlet, such that ice particles in theflow of air can accumulate at the outlet of the conduit, and whereinsaid processing device is configured to adjust the heating power of theheater to substantially prevent liquid water from freezing in theconduit but not substantially melt a threshold level of ice particlesaccumulated in the conduit.
 2. The system of claim 1, wherein the sensorcomprises a sensing element, the sensing element comprising a pressuretap in a wall of the conduit to sense the pressure within the interiorof the conduit.
 3. The system of claim 1, wherein the sensor comprises atransducer, the transducer comprising a differential pressure sensorconfigured to sense the pressure within the interior of the conduit withrespect to a reference pressure.
 4. The system of claim 3, wherein theconduit is a first conduit, the system further comprising a secondconduit, the second conduit comprising a pressure tap configured toprovide the reference pressure.
 5. The system of claim 4, wherein theheater is a first heater configured to heat the first conduit to a firsttemperature, the system further comprising a second heater configured toheat the second conduit to a second temperature, wherein the first andsecond temperatures are associated with a threshold level, whereby aconcentration of ice particles above the threshold level results in theaccumulation of a blockage of the first conduit and a concentration ofice particles below the threshold level results in the melting of theice particles to keep the second conduit substantially ice free.
 6. Thesystem of claim 1, wherein the sensor comprises a pressure sensorsupported within a wall of the conduit, the pressure sensor configuredto sense the pressure within the interior of the conduit, the processingdevice further configured to detect an increase in the pressure withinthe interior of the conduit, the increase being indicative of theaccumulation of ice particles in the conduit.
 7. The system of claim 1,wherein the sensor comprises a 5 temperature sensor supported within awall of the conduit for measuring the temperature of the interior of theconduit, the processing device further configured to detect a change oftemperature within the interior of the conduit when the accumulation ofice particles forms in the conduit.
 8. The system of claim 1, whereinthe sensor comprises a light source and an optical receptive device, thelight source configured to radiate a light beam through a portion of theinterior of the conduit toward the optical receptive device, and whereinthe optical receptive device is configured to detect when the light beamis blocked by the accumulation of ice particles.
 9. The system of claim1, wherein said processing device is configured to adjust the powerlevel of the heater so that the conduit is kept ice-free when theconcentration of ice particles in said flow of air is below thethreshold and is allowed to clog with an accumulation of ice particleswhen the concentration of ice particles in said flow of air is abovesaid threshold.
 10. A method of detecting ice, in the vicinity of anairborne vehicle, the method comprising: heating a conduit at a selectedpower level; allowing a flow of air containing ice particles enteringthe conduit; measuring a parameter within an interior volume of theconduit; and detecting the presence of an accumulation of ice particlesbased on the parameter measured within the interior volume of theconduit, the power level of the heater is adjusted to substantiallyprevent liquid water from freezing in the conduit and low enough tosubstantially avoid melting a threshold level of ice particles thataccumulate within the conduit.
 11. The method of claim 10, furthercomprising: measuring a length of time from detecting a start of theaccumulation of ice particles to detecting a subsequent absence of theaccumulation of ice particles.
 12. The method of claim 11, furthercomprising: measuring conditions of air outside the conduit, theconditions of air outside the conduit including at least one of totalpressure, static pressure, total temperature, and static temperature;and adjusting the heating of the conduit based on the measuredconditions of air outside the conduit.
 13. The method of claim 10,wherein the parameter is selected from the group of parametersconsisting of pressure, temperature, and light beam obstruction.